Fuel stoker



D. R. STAHL Nov. 13,1945.

FUEL STOKER Filed Sept. 15. 1944 I 4%; 2 flII/IIIIIIIIIIIIIIIIIIII), k6' A TTORAIEYS.

atenied ov. 13, 15

s'rrss Metal Specialties 00., Inc., corporation of Wisconsin Milwaukee,Wis., a

Application September 15, 1944, Serial No. 554,183 6 Claims. (oi.110-109) improvements in the construction and operationof mechanicalstokers for feeding fuel such as coal to furnaces or the like.

The primary object of my invention is to provide a new and useful fuelstoker which is simple and compact in construction, and which ismoreover automatic and highly eficient in operation.

Many different types of automatic Or mechanical stokers have heretoforebeen proposed and used with varying degrees of success and for variouspurposes; and the prior fuel stoking devices most extensively employed,were either of the reciprocating plunger or of the rotary screw type. Inthe reciprocating plunger type of stoker, a piston or plunger is causedto reciprocate beneath the lower outlet opening of a fuel supply bin orhopper so a to positively force successive batches of the fuel which aredelivered by gravity past the hopper outlet, through a feed pipe leadinginto the combustion chamber. This plunger type has heretofore beenutilized principally for commercial boiler installations, andconsiderable difilculty has been experienced in causing the plunger toadvance properly beneath the open hopper outlet when the hopper wasladen with an abundant supply of fuel. In the rotary screw type ofstoker, an elongated screw is caused to revolve in the feed pipe leadingfrom the bottom of the supply bin to the combustion chamber so as toconstantly advance a stream of fuel through the straight feed pipe. Thisscrew type has heretofore been employed primarily for household ordomestic heating service, and its construction is such that the feedscrew must be disposed near the combustion chamber since the availablepower will not readily permit feeding from a remote zone through curvedor irregular feed pipes. Both of these prior types of stoking deviceswere also relatively complicated and costly to install and to maintainin operating condition, and were also otherwise objectionable.

It is therefore a more specific object of the present invention toprovide a simplified and more efficient plunger type of stoker which maybe utilized for either domestic or commercial purposes, and which iadapted to feed the fuel for a considerable distance through irregularfeed pamages with minimum power consumption.

Another specific object. of the invention is to provide an exceedinglycompact and durable automatic fuel stoker which will effectively advancethe fuel at any desired rate through a curved or straight feed pipe froma fuel supply bin to a furnace or other combustion device located remotefrom the source of fuel supply.

Still another specific object of my invention is to provide a simplemechanical stoker for fuel such as low grade coal, which. may bemanufactured and sold at moderate cost, and which is safe and reliablein operation and easily installed.

These and other specific objects and advantages of the invention will beapparent from the following detailed description.

A clear conception of the features constituting my present improvement,and of the construction and operation of a typical installationembodying the invention, may be had by referring to the drawingaccompanying and forming a part of this specification wherein likereference char acters designate the same or similar parts in the variousviews.

Fig. 1 is a somewhat diagrammatic part sectional top view of a typicalstoker installation embodying my improvements, showing a fragment of afuel supply bin or hopper;

Fig. 2 is a similar part sectional side elevation of the installationdisclosed in Fig. 1, showing the fuel feeding plunger advancedforwardly-beyond the supply bin outlet opening;

Fig. 3 is a. view similar to that of Fig. 2, but showing the fuelfeeding plunger retracted rearwardly beyond the supply bin outletopening;

Fig. 4 is a diagrammatic perspective view showing the improvedfuelstoker embodied in a typical domestic heating installation; and

Fig. 5 is a fragmentary transverse vertical section through the supplybin outlet, fuel feed pipe, feeding plunger and cut-ofi slide.

While the invention has been shown and described herein as having beenembodied in a reciprocating plunger type of stoker installationespecially adapted for domestic or household heating purposes, it is notmy desire or intention to thereby unnecessarily restrict the scope orthe utility of the improvement.

Referring to the drawing, the typical fuel stoker shown therein by wayof illustration, comprises in general a fuel supply hopper Gr bin anormally containing an abundant supply of fuel such as coal 1 and havinga lower outlet opening 8 adapted to deliver successive batches of thecoal 7 by gravity, into the inlet end ofan elongated fuel feed conduitor pipe 9; a fuel feeding piston or plunge l8 reciprocable within thepipe 9 beneath the bin outlet opening 8; a fuel cut-ofi gate or slide llmovable back and forth in a space between the outlet opening 8 and theplunger III;"a worm wheel I2 and a driving worm I3 therefor, bothjournalled in a housing or casing I4 disposed beyond the rear end of thepipe I; a crank I 5 secured to one side of the worm wheel I2 and beingconnected to the plunger It by means of a piston rod I6; another crankI'I secured to the opposite side of the worm wheel I2 and beingconnected to the slide I l by means of a gate rod I3; and means such asa V.-belt drive I9 fordriving the worm I3 at any suitable speed.

The fuel supply bin 6 may be a hopper located either closely adjacent toor remote from a combustion chamber or fire pot 20 disposed within aheater or furnace 2|; and while the portion of the fuel feed pipe 8within which the plunger I reciprocates should be straight, that portionof the pipe 9 beyond the limits of movement of the plunger I0 may bestraight, or curved, or of any other irregular shape but shouldpreferably have approximately uniform transverse cross-sectional area.The bin 6 may therefore be located a consider distance away from thefurnace 2|, near a window or coal chute, and may be connected to thefire pct 20 by a long gradually curved or straight pipe 9 disposedeither above or below the intervening floor, and the stoker installationmay also be provided with a fan 22 and combustion air supply duct 23 asillustrated in Fig. 4.

The top of the fuel feed pipe 9 is provide with an elongated slot 24extending both forwardly and rearwardly beyond the hopper outlet 8; andthe portion of this slot which extends forwardly beyond the hopper 6, isprovided with a readily removable cover 25 for permitting quick accessto the interior of the feed pipe 9 in order to remove pieces of wood orother large obstructions which may he accidentally deposited within thesupply bin. The piston or plunger III is preferably cylindrical in shapeand should snugly en age the interior of the cylindrical feed pipe 9,and the cut-off plate or slide II is movable in the slot 24 and iscurved to conform with the contour of the pip-e 9 and plunger I0 asclearly shown in Fig. 5. While the slide I I is never movable rearwardlybeyond the hopper outlet opening 8, it is movable forwardly beneath thecover 25, and the front end of the slide II is preferably bevelled orchamfered as indicated in Figs.

2 and 3, so that the advancing plate will cut or sever the mass of coalI.

The housing or casing i4 may be formed of several rigidly but detachablyunited sections readily mounted upon a suitable base 25, and the cranksI5, II have alined outer bearing portions 21, 28 respectively, which aredisposed coaxial with the worm wheel I2 and provide rotary supports forthis main gear Wheel. The driving worm I3 which coacts with the wormwheel I2 within a lower lubricant confining pocket in the casing I4, isrotatably supported in alined bearings 28 carried by the housing; andthe belt drive l9 which is associated with the outer end of the wormshaft 30 may be disposed in any desired direction and connected in anysuitable manner to a driving motoror the like, which may also beutilized to propel the fan 22. The specific disposition and mode ofdriving the belt drive I9 constitutes no essential part of the presentimprovement, and may be varied to suit different conditions.

The inner eccentric end of the lunger reciprocating crank I is providedwith a crank pin H which is rigidly and fixedly attached to the adjacentside of the worm wheel I 2, and the piston rod I3 has one end engagingthe crank pin II while its opposite end is pivotally attached to theplunger III by means of a pin 32. The inner eccentric end of the slidemoving crank I1 is provided with a crank pin 33 which is also rigidlybut adjustably attached to the opposite side of the worm wheel I2, andthe gate rod I8 has an end engaging the crank pin 32 while its oppositeend is pivotally attached to the cut-ofi slide II by means of anotherpin 34. In order' to permit adjustment of the crank pin 33 relative tothe worm wheel I2 and crank pin 3| so as to insure proper timing of themotion of the sliding cuteoff gate relative to the feed plunger III, thepin 33 may be made adjustable, but should be firmly locked in adjustedposition. As shown, the worm wheel I2 is provided with an arcuate slot35 through which the slightly reduced end of the crank pin 33 projects,and a washer 36 and screw 31 are also provided in order to lock the pin33 in any desired position of adjustment within the slot 35. This pinlook? ing assemblag must be so constructed that it will efiect lockingof the crank pin 33 to the worm wheel I2 without clamping the gate rodI8 and without interfering with the normal movement of the piston rodI6; and these rods I8, I8 may be bent or off-set to provide properclearance and to avoid interfering with each other, and aresubstantially concealed within the housing casing I4 and pipe 9 at alltimes.

During normal operation of the improved fuel stoker, the fuel supplyhopper 6 should be constantly provided with an abundant supply of coalI, and the worm I3 should be either continuously or intermittentlyrotated so as to revolve the worm wheel I2 in the direction of thearcuate arrows, whenever fuel feeding is desired. When the feed plungerI0 is in its extreme forward position as in Fig. 2, it has justcompleted a feeding stroke and is about to be withdrawn from beneath thehopper outlet 8, and the cut-off slide and slide will be positioned asshown in Fig. 3

with the plunger I0 fully retracted and the slide II partially advancedand moving forwardly as indicated by the straight arrow again locatedthereabove. The slide II actually begins its cutoff stroke before theplunger III has been fully retracted, due to the angular location of thecrank pins 3|, 33 relative to. the central axis of the worm wheel I2,and while the top of, the plunger I0 is slightly exposed to the coal Iwithin the hopper 6 during its return stroke, this slight exposure isnot objectionable.

During the return stroke of the plunger ID, by virtue of the fact thatthe slide II has been simultaneously withdrawn from beneath the hopperoutlet 8, a charge of coal I gravitates freely through the open slot 24into the pipe-9, and the batch of coal thus delivered by gravitysubstan-' outlet 8 and will move into the portion of the slot 24 beneaththe cover 25; and the forwardly advancing plunger l will then force thepreviously deposited batch of coal 1 which is thus confined within thepipe 9 by the slide II, forwardly through this pipe without permittingthe coal to escape or return into the hopper 8. This feeding cycle isconstantly repeated as long as the rotation of the worm wheel l2continues, and the successive batches of coal I delivered by gravityfrom the hopper 6 into the pipe 9 are forced forwardly so as to providea uniformly advancing stream of coal at the combustion chamber or grate20.

From the foregoing detailed description it will be apparent that mypresent invention provides an improved fuel stoker which besides beingextremely simple, compact and durablein construction, is also highlyefficient in operation and may be utilized to feed a stream of fuelthrough either a straight or a circuitous conduit for considerabledistances. The improved stoker assemblage is not subject to readyclogging and abnormal obstructions may be quickly removed through theforward end of the slot 24 by merely removing the cover 25. The plungerI0 is constantly protested against excessive wear and. is freelyreciprocable within the feed pipe 9 by virtue of the fact that thecut-ofi plate I I relieves the plunger Ill from excessive weight ofmaterial within the hopper 6, during the feeding stroke of the plunger.

.This cut-off plate II also prevents the successive batches of coal Ifrom being returned to the hopper 6 during the feeding stroke of theplunger, and the adjustability of the crank pin 33 enables the operatorto properly time the movement of the slide II so as to insure mostefllcient operation of the unit. The provision of the worm gear drive,besides providing for operation at a desirably low speed, also insuressufficient power for reciprocation of the plunger l0 and slide I I, andthis gear assemblage furthermore reduces the mechanism to relativelysimple form. All parts of the improved apparatus are obviously wellprotested against damage and against possible injury to attendants, andthe various parts should of course be maintained properlylubricated inorder to prolong the life of the apparatus to a maximum. The improvedstoker unit can obviously be manufactured and sold at moderate cost, andreadily installed in conjunction with various types of heatingequipment, and may also be conveniently located relative to the sourceof fuel supply.

It should be understood that it is not desired to limit this inventionto the exact details of construction, or to the precise mode of use,herein shown and described, for various modifications within the scopeof the appended claims may ocour to persons skilled in the art.

Iclaim:

1. In a stoker, a fuel supply hopper having a lower outlet, 9. fuel feedpipe leading away from said hopper outlet and having an elongated slotspanning the outlet,- a plunger movable within said pipe directlybeneath said slot, a slide reciprocable within said slot directlybetween said hopper outlet and said plunger, a member rotatable about anaxis disposed transversely of the direction of movement of said plungerand said slide and having crank pins operatively associated with theopposite sides thereof, and driving connections interposed between saidpins and said plunger and slide respectively for independentlyreciprocating the plunger and slide.

2. In a stoker, a fuel supply hopper having a lower outlet, a fuel feedpipe leading away from said hopper outlet and having an elongated slotspanning and extending forwardly beyond the outlet, a plungerreciprocable within said pipe beneath said outlet and said slot, acut-off plate slidable back and forth beneath said outlet and withinsaid slot directly adjacent to said plunger, a gear rotatable beyond,the rear end of said .pipe about an axis disposed transversely of thesaid outlet to substantially fill said slot and to relieve said plungerfrom the weight of fuel within said hopperwhen saidplunger is movingforwardly, means for simultaneously reciprocating said plunger andmoving said plate, and means for varying the timing of said platemovement.

4. In a stoker, a fuel supply hopper having a lower outlet, a fuel feedpipe extending away from said outlet and having an elongated slotspanning and extending forwardly beyond the outlet, a plungerreciprocable within said pipe directly beneath said slot, a cut-offplate slidable within said slot and-directly between said plunger andsaid outlet to substantially fill said slot and to prevent return offuel from said pipe to said plunger andsaid outlet to substantially fillthe slot, a worm wheel rotatable in the plane of reciprocation of saidplunger, a crank pin at one side of said wheel and being drivinglyconnected to said plunger, and another crank pin at the other side ofsaid wheel and being drivingly connected to said cut-off plate 6. In astoker, a fuel supply hopper having a lower outlet, a fuel conductingpipe having a straight portion provided with an elongated slot extendingacross and beyond said outlet, a

plunger reciprocable within said straight pipe portion directly beneathsaid slot, a cut-off plate reciprocable within said slot between saidplunger and said outlet, a worm wheel rotatable in the plane ofreciprocation of said plunger, a crank pin at one side of said wheel andbeing drivingly connected to said plunger, another crank pin at theother side of said wheel and being drivingly connected to said slide,and means for varying the relative positions of said crank pins withrespect to each other and to said wheel.

DONALD R. S TAHL.

